Résumé
@#Plants contain bioactive compounds and are constantly explored as safer alternatives to conventional insecticides. Despite numerous studies on many plants, information on the insecticidal potential of underutilised plants like tiger nut, Cyperus esculentus L., are scant, although their pharmacological potentials are well known. Hence, this study investigated the larvicidal potential of crude aqueous extracts of two C. esculentus varieties (black and yellow) on the mosquitoes Aedes aegypti (L.) and Culex quinquefasciatus (Say). Mosquito larvae were exposed to C. esculentus crude extracts using the larval bioassay technique of the World Health Organization. Differential larvicidal responses were observed in the test mosquitoes and extracts of Black Dried Tiger nuts (BDT) were more larvicidal than Yellow Dried Tiger nuts (YDT). Acute larval toxicity of the extracts was more pronounced on Cx. quinquefasciatus than Ae. aegypti. The results indicate the potential of C. esculentus (particularly BDT) as a source of mosquito bioinsecticide and merits further studies as a safer alternative to conventional insecticide-based vector control.
Résumé
@#Storage of dengue virus (DENV) culture stocks in -80°C is a common laboratory practice to maintain the viability of the virus for long-term usage. However, the efficiency of this method could still be hindered by multiple factors. In our laboratory, we observed a constant and substantial deterioration in the titer of DENV in Vero culture supernatant stored in -80°C. Such incident had badly hampered the laboratory work and prompted an investigation to determine the cause. DENV isolates representing all four serotypes were propagated and the culture supernatants were harvested and stored in aliquots of original stock and 10 fold dilutions (10-1 -10-4). DENV titer in these stocks was determined prior to storage and reassessed on the third and sixth month of storage by focus forming unit assay (FFUA). The result demonstrated a constant preservation of titer ranging from 104 ffu/ml to 105 ffu/ml in the diluted DENV virus culture stocks of 10-1, and 10-2 of DENV1-4, a minor reduction of titer from 103 ffu/ml to 102 ffu/ml at dilution 10-3 for DENV4 only and complete deterioration in undiluted culture stock and lower dilution (10-4) within 6 months of storage in -80°C for all serotypes. It is recommended that propagated DENV in Vero cells are stored in 10 fold dilutions as compared to the original form to preserve the titer for long-term usage.
Résumé
Glutathione S-transferases (GSTs) are multifunctional enzymes involved in detoxification of xenobiotic compounds in many insect groups. This work investigated the expression of GSTs in Aedes albopictus by using affinity chromatography and proteomic analysis. The study compared the expression of GSTS isoforms in larvae of three Ae. albopictus strains (susceptible (VCRU) strain, field Kuala Lumpur (KL) strain and laboratory permethrintreated strain). The study demonstrated that the expression of sixteen isoforms (GSTS1-1, GSTS1-4, GSTS1-3, GSTS1-4, GSTD1-3, GSTD1-2, GSTD1-5, GSTD1-6, GSTD1-7, GSTD1-8, GSTD1-9, GSTD1-10, GSTD1-11, GSTT, GSTD1-12, and GSTD1-13) were significantly increased in the field KL strain (p0.05). However, while comparing the expression of GST isoforms in field KL larvae and laboratory permethrin-treated strain, the same pattern was observed for all the GSTs especially for Theta and Sigma class (p>0.05). In Delta class, only GSTD1-1, GSTD1-9, GSTD1-11, GSTD1- 12 and GSTD1-13 shows significant difference in expression between these two strain (p<0.05). This comparative data on GST expression in Ae. albopictus can be useful database to identify possible underlying mechanisms governing insecticide resistance by GSTs.